Method and apparatus for high heat flux heat transfer

ABSTRACT

The subject invention pertains to a method and apparatus for high heat flux heat transfer. The subject invention can be utilized to transfer heat from a heat source to a coolant such that the transferred heat can be effectively transported to another location. Examples of heat sources from which heat can be transferred from include, for example, fluids and surfaces. The coolant to which the heat is transferred can be sprayed onto a surface which is in thermal contact with the heat source, such that the coolant sprayed onto the surface in thermal contact with the heat absorbs heat from the surface and carries the absorbed heat away as the coolant leaves the surface. The surface can be, for example, the surface of an interface plate in thermal contact with the heat source or a surface integral with the heat source. The coolant sprayed onto the surface can initially be a liquid and remain a liquid after absorbing the heat, or can in part or in whole be converted to a gas or vapor after absorbing the heat. The coolant can be sprayed onto the surface, for example, as a stream of liquid after being atomized, or in other ways which allow the coolant to contact the surface and absorb heat. Once the heat is absorbed by the coolant, the coolant can be transported to another location so as to transport the absorbed heat as well.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application is a continuation of U.S. Ser. No. 11/305,525,filed Dec. 16, 2005, now U.S. Pat. No. 7,654,100 which is acontinuation-in-part of U.S. Ser. No. 10/348,850, filed Jan. 22, 2003,now U.S. Pat. No. 6,993,926, which is a continuation-in-part of U.S.Ser. No. 10/115,510, filed Apr. 2, 2002, now U.S. Pat. No. 6,571,569,which claims the benefit of U.S. Ser. No. 60/350,857, filed Jan. 22,2002; U.S. Ser. No. 60/350,871, filed Jan. 22, 2002; U.S. Ser. No.60/350,687, filed Jan. 22, 2002; U.S. Ser. No. 60/290,368, filed May 12,2001; U.S. Ser. No. 60/286,288, filed Apr. 26, 2001; U.S. Ser. No.60/286,771, filed Apr. 26, 2001; and U.S. Ser. No. 60/286,289, filedApr. 26, 2001, each of which is incorporated herein by reference in itsentirety. U.S. Ser. No. 10/348,850, filed Jan. 22, 2003, now U.S. Pat.No. 6,993,926, is also a continuation-in-part of U.S. Ser. No.10/342,669, filed Jan. 14, 2003, now abandoned which claims the benefitof U.S. Ser. No. 60/353,291, filed Feb. 1, 2002, and U.S. Ser. No.60/398,244, filed Jul. 24, 2002, each of which is incorporated herein byreference in its entirety. U.S. Ser. No. 11/305,525 also claims benefitof U.S. provisional patent application U.S. Ser. No. 60/654,023, filedFeb. 17, 2005, which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

In recent years, attention has been focused on methods of high heat fluxremoval at low surface temperatures. This is due in large part to theadvancing requirements of the electronics industry that prevent hightemperature heat transfer due to the operating conditions ofelectronics. Though the heat transfer process is very complex and stillnot completely understood, many evaporative spray cooling experimentshave been performed which indicated the high heat removal capability ofthis cooling technique. The spray technique generally works in thefollowing way; a spray nozzle is used to atomize a pressurized liquid,and the resulting droplets are impinged onto a heated surface. A thinfilm of liquid is formed on the heat transfer surface in which nucleateboiling takes place. The droplet impingement simultaneously causesintense convection and free surface evaporation. When a liquid with ahigh latent heat of vaporization (such as water) is used, over 1 kW/cm²of heat removal capability has been demonstrated.

The temperature of the cooled surface is determined by the boiling pointof the liquid. Since the resulting heat transfer coefficient is verylarge (50,000 to 500,000 W/m²C) the surface temperature will be only afew degrees centigrade above the boiling point of liquid.

This type of cooling technique is most appropriately implemented whenused to cool high heat flux devices such as power electronics, microwaveand radio frequency generators, and diode laser arrays.

Prior art describes processes and devices related to cooling of small,individual electronic chips. This can be seen in, for example, U.S. Pat.Nos. 5,854,092; 5,718,117; and 5,220,804. This prior art uses a liquidspray to cool individual electronic components, or an array of theseindividual components located at discrete distances from each other.Since the electronic components (the heat sources) are individualdevices with spaces between, the liquid spray cones do not overlap orinteract with each other. The typical size of an electronic chip is 2cm² in area and is spaced at a distance of 0.5 to 1 cm. This allows theprior art to cool these chips with an impinging spray withoutinterfering with the spray process of the surrounding chips.

As stated above, diode laser arrays and microwave generators are devicesthat can be cooled with this type of impinging spray technology. Currentmarket forces are driving these devices to increased power and sizerequirements. As a result, high heat flux devices are now being designedwith surface areas much larger than 2 cm². New high heat flux deviceswill be 100 cm² to 1000 cm². The entire large surface area will need tobe cooled at the same high heat flux rate as the small devices were inthe prior art. However, the prior art does not detail a method to coolsuch a large device. Rather, the prior art only details a method to coolseveral small individual devices.

It may be thought that a large surface could be cooled with an array ofnozzles spraying down on the large surface in the same way a singlenozzle sprays down on a small surface, as shown in the prior art.However, it has been shown in a study with air jet impingement thatscaling in this way is not possible. Instead, the effectiveness of thejets or sprays in the center of the array interact with each other in away that considerably reduces the ability to transfer heat. This is aresult of the fluid flow accumulating as the fluid moves outward fromthe stagnation point. A good portion of the impinging droplets arevaporized with this system, however, this is not so for all the liquid.The remaining liquid will flow off the heated surface and be returned tothe pump. When the surface is large, the fluid from the nozzles at thecenter of the surface will need to travel across the entire surfacebefore exiting at the edges. This can be called the “spray liquidrun-off problem.”

BRIEF SUMMARY OF THE INVENTION

The subject invention pertains to a method and apparatus for high heatflux heat transfer. The subject invention can be utilized to transferheat from a heat source to a coolant such that the transferred heat canbe effectively transported to another location. Examples of heat sourcesfrom which heat can be transferred from include, for example, fluids andsurfaces. The coolant to which the heat is transferred can be sprayedonto a surface which is in thermal contact with the heat source, suchthat the coolant sprayed onto the surface in thermal contact with theheat absorbs heat from the surface and carries the absorbed heat away asthe coolant leaves the surface. The surface can be, for example, thesurface of an interface plate in thermal contact with the heat source ora surface integral with the heat source. The coolant sprayed onto thesurface can initially be a liquid and remain a liquid after absorbingthe heat, or can in part or in whole be converted to a gas or vaporafter absorbing the heat. The coolant can be sprayed onto the surface,for example, as a stream of liquid after being atomized, or in otherways which allow the coolant to contact the surface and absorb heat.Once the heat is absorbed by the coolant, the coolant can be transportedto another location so as to transport the absorbed heat as well.

The subject invention pertains to a method and apparatus for coolingsurfaces and/or devices. In a specific embodiment, the subject inventioncan incorporate a spray nozzle and a cooling/electronic interfacesurface. The spray nozzle may use pressurized liquid (commonly known aspressure atomizer nozzles), pressurized liquid and pressurized vapor(commonly known as vapor assist nozzles), and/or pressurized vapor(commonly known as vapor blast or vapor atomizer nozzles) to develop theatomized liquid spray used in the cooling process.

The subject invention also relates to a heat transfer apparatus havingan enhanced surface which can increase the rate of heat transfer fromthe surface to an impinging fluid. The subject enhanced surface can beincorporated with any of the heat transferred surfaces disclosed in thesubject patent application or incorporated with other heat transfersurfaces. The subject invention also pertains to heat transferapparatus, such as heat transfer plates, which incorporate the subjectenhanced surfaces. The subject enhanced surfaces can also be utilizedfor heat desorption from a surface.

FIGS. 12A-12E show specific examples of surface enhancements that can beutilized in accordance with the subject matter. The subject surfaceenhancements shown in FIGS. 12A-12E, and/or other similar surfaceenhancements, can be utilized with any embodiment of the subjectinvention incorporating a heat transfer surface.

In a specific embodiment, the cooling/electronic interface surface canbe compartmentalized such that spray entering one compartment is impededfrom crossing over to adjacent compartments. In a further specificembodiment, a plurality of nozzles can each spray into one of aplurality of compartments such that spray from each individual nozzle isapplied to a specific target area. For example, each nozzle may sprayone compartment. The excess liquid which enters each compartment canthen be forced out of the compartment in a counter-parallel flow fromthe spray direction rather than a perpendicular flow as in prior art, soas to correct the liquid run-off problem. The shape and depths of thecompartments can vary according to the type of nozzle used to atomizethe liquid coolant. Preferably, the subject compartments incorporateside walls which can redirect the exiting flow in a pattern that is notperpendicular to the incoming flow.

The atomized spray can be directed onto the rear surface of thecompartmentalized interface plate. The spray is preferably positioned tocreate the most even application of atomized liquid onto the entire rearsurface. The liquid can be sprayed at a temperature near its boilingpoint. Thus, when the liquid hits the heated surface in the rear of thecompartment, the liquid can begin to boil. The heat from theelectronics, or other heat source, is transferred through the interfaceinto the boiling liquid spray at a very high rate. The created coolantvapor and excess liquid exit the compartment in a direction that is notperpendicular to the incoming flow. Under the operating conditions of anopen loop system, the boiling point of the liquid coolant must be atambient pressure since the evaporating environment is exposed to theambient. Under these conditions, the heat removed by the developed vaporis released to the atmosphere. However, not all vaporized coolants canbe responsibly released to the atmosphere, due, for example, toenvironmental concerns. In addition, coolants with boiling points otherthan ambient may be preferred. Accordingly, specific embodiments of thesubject invention can be operated in a closed loop.

In a closed loop system, the interface plate can be located within asealed housing so that the spray and the resultant vapor is trappedwithin the sealed housing. Under this condition, the pressure within thehousing can influence the boiling point of the coolant and the operatingtemperature. As the coolant vaporizes, it carries the heat from, forexample, electronics, away from the interface plate. Since the system isnow closed, the vapor can be condensed and the heat released out of thehousing through a condenser. The condenser can incorporate, for example,a standard heat exchanger or can operate via a sub-cooled mist of thecoolant sprayed within the housing. The mist can be sub-cooled below thesaturation temperature of the coolant within the housing via an externalheat exchanger. As the sub-cooled liquid spray contacts the saturatedvapor, heat is transferred to the spray and the vapor condenses on theliquid droplets and flows to a liquid reservoir.

The coolant can be drawn from the liquid reservoir, for example, by aliquid pump or via venturi action of a vapor atomizer nozzle. The liquidthen flows through the nozzle and is once again sprayed onto theinterface plate. The circulation of the coolant within the closedprocess depends on the type of atomizer used. If pressure atomizernozzles are used, then a liquid pump can suffice. If vapor assistnozzles or vapor atomizer nozzles are used, then both a vapor compressorand a liquid pump can be used in the circulation of the coolant.

Typically, the heat gained by the liquid in the closed system istransferred to a refrigerant of a vapor compression cycle via a heatexchanger. The vapor compression cycle increases the temperature of thenow warmer refrigerant and allows it to release the heat to theenvironment. This is commonly known as the chiller loop.

An additional feature can be added to the closed system that combines itwith a vapor compression cycle without the heat exchanger interfacebetween the two loops. This combination involves using a refrigerant asthe coolant in both loops. Under this scenario, liquid refrigerant canbe atomized onto the interface plate. Vapor and excess liquidrefrigerant can be expelled from the compartment and flow into thehousing. The saturated vapor can be removed from the housing with avapor compressor and can be compressed to a temperature above ambienttemperature of the final heat sink, for example atmospheric air. The nowsuperheated vapor can flow through a heat exchanger releasing the heatto the final heat sink. As the heat is released, the superheated vaporcondenses to liquid refrigerant. As is common to vapor compressioncycles, the higher pressure saturated liquid can flow through anexpansion valve. The liquid is allowed to expand to the pressure of thehousing, cools to its saturation temperature within the housing, andflows to the liquid reservoir ready to begin the process once again.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic illustration of a spray-nozzle spraying theatomized liquid coolant into a cell of a cooling plate in accordancewith a specific embodiment of the subject invention.

FIGS. 2A-2C show specific embodiments of a cooling plate having aplurality of cells, or compartments, in accordance with a specificembodiment of the subject invention.

FIG. 3 shows a manifold of spray nozzles in accordance with a specificembodiment of the subject invention.

FIG. 4 shows the manifold of spray nozzles from FIG. 3 aligned with theplurality of cells from FIG. 2.

FIG. 5 shows an embodiment of the subject invention incorporating aclosed loop structure.

FIG. 6 shows an embodiment of the subject invention in which anevaporative spray cooling loop is combined with a vapor compressioncycle.

FIG. 7 shows a specific embodiment of a heat exchanger in accordancewith the subject invention.

FIG. 8 shows an embodiment of the subject invention in which anevaporative spray cooling loop is combined with a vapor compressioncycle.

FIG. 9 shows an embodiment of the subject invention in accordance withthe embodiment shown in FIG. 8, further incorporating an accumulator.

FIG. 10A shows an embodiment of the subject invention in which anevaporative spray cooling loop is combined with a vapor compressioncycle, further incorporating an accumulator and a phase separator.

FIG. 10B shows an embodiment of the subject invention in which anevaporative spray cooling loop is combined with a vapor compressioncycle, further incorporating a phase separator.

FIG. 11 shows a schematic diagram of a cooling system in accordance withthe subject invention.

FIGS. 12A-12E show a heat transfer surface incorporating surfaceenhancement in accordance with the subject invention.

FIG. 13 shows a schematic diagram of a cooling system in accordance withthe subject invention, which incorporates a thermal energy storage unit.

FIG. 14 shows a diagram key for FIGS. 15-31.

FIG. 15 shows an embodiment in accordance with the subject inventionincorporating a condenser and compressor.

FIG. 16 shows an embodiment in accordance with the subject inventionincorporating a condenser, phase separator, and two phase pump.

FIG. 17 shows an embodiment in accordance with the subject inventionincorporating a condenser, phase separator, and two phase pump.

FIG. 18 shows an embodiment in accordance with the subject inventionincorporating a phase separator, condenser and two phase pump.

FIG. 19 shows an embodiment in accordance with the subject inventionincorporating a liquid pump, vapor compressor, phase separator, andcondenser.

FIG. 20 shows an embodiment in accordance with the subject inventionincorporating a two phase pump, condenser, and phase separator.

FIG. 21 shows an embodiment in accordance with the subject inventionincorporating a liquid pump, vapor compressor, condenser, and phaseseparator.

FIG. 22 shows an embodiment in accordance with the subject inventionincorporating a liquid pump, vapor compressor, condenser, and phaseseparator.

FIG. 23 shows an embodiment in accordance with the subject inventionincorporating a condenser, liquid pump, vapor compressor, and phaseseparator.

FIG. 24 shows an embodiment in accordance with the subject inventionincorporating a phase separator for inputting to a spray nozzle, phaseseparator accepting exhaust from the spray nozzle, liquid pump, vaporcompressor, and condenser.

FIG. 25 shows an embodiment in accordance with the subject inventionincorporating a phase separator for inputting to a spray nozzle, phaseseparator accepting exhaust from the spray nozzle, liquid pump, twophase pump, and condenser.

FIG. 26 shows an embodiment in accordance with the subject inventionincorporating a phase separator for inputting to a spray nozzle, phaseseparator accepting exhaust from the spray nozzle, condenser, liquidpump, and vapor compressor.

FIG. 27 shows an embodiment in accordance with the subject inventionincorporating a phase separator for inputting to a spray nozzle, twophase pump, phase separator accepting two phase flow from the two phasepump, and condenser.

FIG. 28 shows an embodiment in accordance with the subject inventionincorporating a phase separator for inputting to a spray nozzle, acondenser, a phase separator accepting two phase flow from thecondenser, a liquid pump, and a vapor compressor.

FIG. 29 shows an embodiment in accordance with the subject inventionincorporating a phase separator for inputting to a spray nozzle, vaporcompressor, phase separator accepting two phase flow from the vaporcompressor, and condenser.

FIG. 30 shows an embodiment of a condenser expansion valve in accordancewith the subject invention.

FIG. 31 shows an embodiment to sub-cool liquid in accordance with thesubject invention.

DETAILED DESCRIPTION

The subject invention pertains to a method and apparatus for high heatflux heat transfer. The subject invention can be utilized to transferheat from a heat source to a coolant such that the transferred heat canbe effectively transported to another location. Examples of heat sourcesfrom which heat can be transferred from include, for example, fluids andsurfaces. The coolant to which the heat is transferred can be sprayedonto a surface which is in thermal contact with the heat source, suchthat the coolant sprayed onto the surface in thermal contact with theheat absorbs heat from the surface and carries the absorbed heat away asthe coolant leaves the surface. The surface can be, for example, thesurface of an interface plate in thermal contact with the heat source ora surface integral with the heat source. The coolant sprayed onto thesurface can initially be a liquid and remain a liquid after absorbingthe heat, or can in part or in whole be converted to a gas or vaporafter absorbing the heat. The coolant can be sprayed onto the surface,for example, as a stream of liquid after being atomized, or in otherways which allow the coolant to contact the surface and absorb heat.Once the heat is absorbed by the coolant, the coolant can be transportedto another location so as to transport the absorbed heat as well.

In a specific embodiment, the subject invention relates to a coolingprocess which begins, as shown in FIG. 1, by attaching a heat sourcesuch as a high power electrical device to surface 1 of interface plate3. Interface plate 3, as in the other embodiments of the subjectinvention, can be a separate plate in thermal contact with a heatsource, or can be integral with a heat source, for example, a wall of adevice producing heat which needs to be removed. Referring to thespecific embodiment shown in FIG. 1, spray nozzle 5 atomizes liquidcoolant into a spray compartment in a uniform spray pattern 7. If spraynozzle 5 is a pressure atomizer nozzle, then pressured liquid coolantcan be supplied by a pressurized liquid source 9. This source can be,for example, a compressed storage tank or a supply pump drawing liquidcoolant from a reservoir. If spray nozzle 5 is a vapor atomizing nozzle,then pressurized vapor can be supplied to spray nozzle 5 via compressedvapor source 11. The compressed vapor source 11 can be, for example, acompressed vapor storage tank or a vapor compressor. The flow of vaporthrough the vapor atomizing nozzle 5 can create a venturi draft on theliquid port such that the pressurized liquid source 9 need not bepressurized but, rather, can be, for example, a reservoir of liquidcoolant. If spray nozzle 5 is a vapor assist nozzle then both thepressurized liquid source 9 and the pressurized vapor source 11 can besupplied to nozzle 5. The pressurized sources 9 and 11 can be supplied,for example, via pressurized storage tanks and/or a liquid pump and/or avapor compressor.

A specific embodiment of an interface plate 3 in accordance with thesubject invention is shown in FIG. 2A. The cooling plate 3 shown in FIG.2A incorporates a set of partition walls 21 that protrude from theheated surface 2 of interface plate 3 and form subsections, or cells 23.In a preferred embodiment, each cell 23 has a surface area on surface 2of about 0.5 to 2 cm². The walls can give the interface plate 3 an “icecube tray” look, and protrude, for example, about 0.2 cm to 2 cm fromsurface 2. The shape of the subsections, or cells, can be, for example,circular, square, or other polygonal shapes. In a specific embodiment,the subsections can be honeycomb shaped. The surface area of the cellsand the height to which the cell walls 21 protrude from surface 2 arepreferably selected such that the coolant which is sprayed into thecell, after removing heat from surface 2, can escape from the cellwithout interfering with the heat transfer occurring in adjacent cells.Partition walls 21 shown in FIGS. 1 and 2A-2C can be used to reduce, orsubstantially eliminate, the flow of coolant incident on surface 2 outof cell 23 and into adjacent cells and reduce, or substantiallyeliminate, the flow of coolant incident on surface 2 of adjacent cellsinto cell 23. The coolant departing the subsection, or cell, in gas orvapor form can escape to the environment or, in the case of a closedsystem can be captured, converted back to liquid form, and resprayedonto surface 2. The coolant departing the subsection in liquid form canflow past the end of partition walls 21, be captured, optionally cooled,and resprayed onto surface 2. Other flow patterns, such as along the endof partition wall 21, can occur depending on the various parameters ofthe system.

The number of compartments can be determined by the area of eachcompartment, the widths of the compartment walls 21, and the total areaof desired cooling. Each compartment can have one or more nozzles whichspray into the compartment. In a specific embodiment, the one or morenozzles spray onto the heated surface 2 at the bottom of thecompartment. FIG. 2B shows a partition wall pattern which canaccommodate more than one spray nozzle spraying into each cell 23. Eachcell 23 shown in FIG. 2B can accommodate, for example, four spraynozzles. Although the partition walls 21 shown in FIGS. 2A-2C form arectangular or square pattern and are of essentially constant thicknessfrom end to end, other patterns can be utilized and the thickness ofpartition walls 21 can vary, depending on the application. For example,a hexagonal or other polygonal pattern, or even circular cells 23, maybe preferred. In addition, the partition walls 21 may have an increasedthickness near surface 2 to enhance the redirecting of the coolant flowout of the cell. Such increased thicknesses near surface 2 can provide acurved shaped wall such that coolant flowing on surface 2 and reachingthe wall experiences a curved surface to transition from surface 2 ontothe side of wall 21 rather than an abrupt corner between wall 21 andsurface 2.

In a specific embodiment of the subject invention, partition walls 21can be removed and a plurality of spray nozzles can spray surface 2 suchthat the spray of the adjacent nozzles does not overlap and the liquidcoolant sprayed onto surface 2 travels along the surface of surfaceliquid 2 until running into the liquid coolant sprayed onto surface 2 byan adjacent nozzle. As the flows of coolant from adjacent spray nozzlescollide, the collision can change the momentum of the flows such that atleast a portion, and preferably essentially all, of the combined flowflows away from surface 2. Accordingly, after the collision of adjacentflows, a substantial portion of the combined flow's momentum can then bein a direction perpendicular to surface 2. In addition, the combinedflow may have a certain amount of momentum parallel to surface 2, suchthat the combined flow flows as a river, above surface 2, near theportion of surface 2 where the collision of the two adjacent flowsoccurs. The direction of these river flows depends, among other factors,on the spray patterns of the adjacent spray nozzles, the speed of thespray, and the form of the coolant being sprayed onto surface 2. Whenpartition walls are present, how far out partition walls 21 protrudefrom surface 2 can impact how the coolant which impinges on surface 2flows away from cell 23. Partition walls 21 can protrude sufficientlyfar such that coolant impinging on surface 2, upon reaching the end ofthe partition wall, continues away from interface plate 3.Alternatively, if partition walls are made to protrude less, coolantreaching the ends of the partition walls can, at least in part, flow ina river flow along the ends of the partition walls. Again, the exactnature of how the coolant flows after reaching the ends of the partitionwalls is dependent, among other factors, on the spray patterns of theadjacent spray nozzles, the speed of the spray, and the size and form ofthe coolant being spraying onto surface 2.

A manifold of spray nozzles in accordance with a specific embodiment ofthe subject invention is shown in FIG. 3. The spray nozzles 5 can beattached to manifold 4 with liquid inlet port 32 and vapor inlet port34. A specific assembly of spray nozzle manifold 4 and compartmentalizedinterface plate 3 is shown in FIG. 4. In the embodiment shown in FIG. 4,each spray nozzle of the manifold of spray nozzles sprays coolant into acorresponding cell of the plurality of cells 23. In an alternativeembodiment, more than one spray nozzle can spray coolant into a singlecell. FIGS. 2B and 2C show embodiments of interface plates which canaccommodate more than one spray nozzle per cell or compartment.

In alternative embodiments, surface 2 can be a surface of a heat sourcesuch as an electronics circuit chip, power electronic device, microwaveor radio frequency generator, or diode laser array. In the situationwhere surface 2 is a surface of a heat source, partition walls 21 can beintegral with the surface 2 of the heat source, or partition walls 21can be part of a separate interface plate 3 without a surface 1 orsurface 2 such that the partition walls themselves are the interfaceplate 3. In the latter case, interface plate 3, comprising partitionwalls 21 can be pressed against surface 2 of the heat source. Ifdesired, a means for creating a seal between the partition walls 21 andsurface 2. Such a sealing means can reduce, or substantially eliminate,flow of coolant between the ends of partition walls 21 and surface 2. Ina specific embodiment, such means for sealing can be attached to theends of partition walls 21 which will contact surface 2 of the heatsource, such that as the ends of partition walls 21 are pressed againstsurface 2 a seal between the ends of partition walls 21 and surface 2 iscreated so as to reduce, or substantially eliminate, flow of coolantbetween the ends of partition walls 21 and surface 2. In a specificembodiment, interface plate 3 can be fixedly positioned with respect toa manifold of spray nozzles such that the manifold-interface platecombination can be brought into contact with a surface 2 of a heatsource and operated to remove heat from surface 2 of the heat source.

Spray nozzles in accordance with the subject invention can spray, forexample, jet sprays of coolant and or atomized sprays of coolant. Jetspray nozzles can spray liquid coolant in, for example, a solid cone orsheet such that the coolant hits the surface and breaks up. The coolantcan then flow across surface 2. Atomizing spray nozzles can atomize thecoolant into droplets of appropriate size and can provide the dropletswith an appropriate velocity. Although a variety of droplet sizes andvelocities can be utilized in accordance with the subject invention, ina specific embodiment an atomizing spray nozzle can be used whichproduces droplets having mean diameters in a range from about 10 micronsto about 200 microns and provides the droplets a velocity in a rangefrom about 5 meters per second to about 50 meters per second.Preferably, the size and velocity of the particles are such that theeffects of gravity are negligible. Utilizing small droplets at highvelocity can allow the method and apparatus of the subject invention tobe used with heated surfaces 2 oriented in a variety of directions (e.g.vertical or horizontal) and can make it easier to provide coverage ofthe surface 2 with the spray coolant.

With high velocity spraying, a layer of coolant can form on surface 2such that boiling occurs within the layer. As boiling occurs, bubbleswill tend to grow, causing the portion of surface 2 under the bubble tonot be wetted. However, the constant bombardment of liquid spraydroplets onto surface 2 can help displace the bubbles and prevent thebubbles from growing larger. In this way, a larger portion of surface 2can be kept wetted so as to increase heat transfer. Spray patterns fromatomizing spray nozzles in accordance with the subject invention can be,for example, round, square, rectangular (which can be referred to as afan spray pattern), or other shape appropriate to the shape of surface 2and/or the partition walls 21. Preferably, for each shape spray pattern,an even spray pattern is achieved by the atomizing spray nozzle.

The subject method and apparatus can be utilized as an open system wherethe coolant which is converted to gas or vapor upon spraying ontosurface 2 can escape, for example, into the environment. In such an opensystem, the coolant which remains in liquid form can be collected andreused. If desired, the collected liquid coolant can be cooled beforereuse, or re-spraying back onto surface 2. The subject method andapparatus can also be utilized as a closed system where at least aportion, and preferably essentially all, of the coolant which isconverted to gas or vapor upon spraying onto surface 2, as well as thecoolant which remains in liquid form, can be collected and reused. In aspecific embodiment, the subject method can utilize a sealed housing,which can maintain a pressure different from the environment, to containthe coolant and collect and process the coolant.

Referring to FIG. 5, a specific embodiment with a closed loop cycle isshown. Spray manifold 4 can be placed within a sealed housing 27. Sealedhousing 27 can be any of a variety of shapes and topologies andencapsulates a region where the pressure can be controlled. Interfaceplate 3 can function as one of the walls of housing 27. The coolingprocess can be substantially similar to the process described withrespect to FIG. 1. The flow pattern can be varied and can vary with thetype of nozzle used. In a specific embodiment, pressure atomizer nozzlescan be used. Referring back to FIG. 5, liquid coolant can be drawn fromreservoir 58 and pressurized via liquid coolant pump 8. Liquid coolantpump 8 can send pressurized liquid coolant into spray nozzle manifold 4.The liquid coolant can be distributed into the array of spray nozzles 5and sprayed into compartments 23 of the interface plate 3. Interfaceplate 3, as in the other embodiments of the subject invention, can be aseparate plate in thermal contact with a heat source, or can be integralwith a heat source, for example, a wall of a device producing heat whichneeds to be removed. Due to heat supplied by a heat source to surface 1,at least a portion of the liquid coolant can vaporize as it contactssurface 2 of compartment 23. The vapor can then flow into the housing27. The embodiment shown in FIG. 5 can also be implemented without spraymanifold 4 and, instead, with other nozzle options, for example a singlenozzle.

To condense the vapor and remove the heat acquired from the heat source,a condenser can be placed within the housing. The condenser can consistof a standard vapor to liquid heat exchanger with cold liquid suppliedvia a vapor compression cycle to the liquid ports of the heat exchanger.The warm vapor condenses on the heat exchanger, releasing its heat tothe vapor compression cycle and flows into the reservoir.

A more efficient method of condensing the vapor and removing the heatinvolves adding another set of spray nozzles 56 to spray sub-cooledliquid coolant into the housing. A portion of the pressurized liquidfrom pump 8 can be sent to a heat exchanger 54 via tubing 52, ratherthan to manifold 4, to sub-cool a portion of the pressurized liquidcoolant. Heat exchanger 54 can be, for example, a liquid-to-liquid heatexchanger cooled with liquid on one side of the exchanger. Liquid from avapor compression cycle can be used for this purpose. If the saturationtemperature of the housing 27 is above ambient, the heat exchanger 54can be a vapor-to-liquid heat exchanger cooled by ambient air. Thesub-cooled liquid coolant can then be directed to one or more pressureatomizer nozzles 56 and sprayed within the housing. The saturated vaporgenerated within the housing can contact the sub-cooled droplets. Thesaturated vapor can condense on the sub-cooled droplets to form largerdroplets, which can flow into the reservoir to be reused in the process.

Referring to FIG. 6, in another specific embodiment of the subjectinvention, the evaporative spray cooling loop can be combined with thevapor compression cycle. In contrast with the closed loop systempreviously described with reference to FIG. 5, which used a coolant inthe evaporative spray cooling loop to transfer the heat from the heatsource to a vapor compression cycle via heat exchanger 54, in theembodiment shown in FIG. 6, the heat exchanger can be removed and asingle coolant used. The use of a single coolant in this embodiment canallow for a more efficient and compact system.

Again referring to FIG. 6, the system can utilize a sealed andpressurized evaporator housing 27. A heat source can be thermallycoupled to surface 1. Heat coupled to surface 1 can be removed by theevaporation of the coolant sprayed onto surface 2 of the interfaceplate. Interface plate 3, as in the other embodiments of the subjectinvention, can be a separate plate in thermal contact with a heatsource, or can be integral with a heat source, for example, a wall of adevice producing heat which needs to be removed. The vapor generated bythe cooling process can be pulled from housing 27 via vapor compressor28. The vapor can enter vapor compressor 28 through tubing 53 and bepressurized. The vapor compression can have two stages: one for poweringone or more spray nozzles 5 through tubing 57 and another to completethe vapor compression cooling cycle through tubing 59. In a specificembodiment, this two stage design can be accomplished with a two stagecompressor 28 with outlet ports designed to discharge the compressedvapor at the desired compression ratios. In an alternative embodiment,two compressors can be utilized: the first one compressing to thepressure required to power the spray nozzle and the second forcompressing the vapor to desired pressure to complete the vaporcompression cycle. In another alternative embodiment, a single stagecompressor can be used which compresses all the vapor to the desiredpressure for the vapor compression cycle and which bleeds off theportion needed for the spray nozzle through an expansion valve, turbine,or nozzle.

The pressurized vapor used to power the one or more spray nozzles 5 canport directly back into the spray nozzle manifold. Depending on thenozzle used, the liquid from the reservoir 58 can either be pumped tothe liquid port of the spray nozzle manifold or sucked through it viaventuri action, for example through tubing 61. The second port fromcompressor 28 can discharge vapor at the desired pressure to completethe vapor compression cooling cycle. The superheated compressed vaporcan then be channeled to condenser 31. Within the condenser, which canutilize, for example, an air, gas, or liquid heat exchanger, the hightemperature compressed vapor can be cooled and condensed to a saturatedliquid. The cooled saturated liquid can exit the condenser and bechanneled to an expansion valve, turbine, or nozzle 33. The expansionvalve, turbine, or nozzle 33 can cause the pressure of the saturatedliquid coolant to drop to the pressure and corresponding saturationtemperature of the evaporator housing 27. The mixed quality liquid canthen exit the expansion valve, turbine, or nozzle 33 and be channeled tothe liquid reservoir 58 waiting to be reused. Using a turbine ratherthan an expansion valves would allow the recapture of the energynormally lost through the expansion valves. Using a nozzle can allow fordirect spraying of the liquid coolant onto heat transfer surface 2 if,for example, a pressure atomizer nozzle is used. Alternatively, withrespect to the embodiment shown in FIG. 6, a phase separator 50 as shownin FIG. 10B could be placed after expansion valve 33 and reservoir 58such that tubing 57 could receive vapor coolant from the phase separatorrather than compressor 28.

Example 1 Method for Spray Impingement Heat Exchanger

The system described in this example can utilize the technique ofspraying coolant onto a surface in order to transfer heat from thesurface to the coolant and can also utilize the spraying of coolant ontoa surface to transfer heat from the coolant to the surface. By sprayinga first, hot, coolant onto a first surface of a dividing wall and asecond coolant onto an opposite surface of the dividing wall, heat canbe transferred from the first coolant to the second coolant. In thisexample, a housing with a dividing wall, two fluid spray nozzleassemblies and two fluid outlets can be utilized. The dividing wall inthe housing separates the two flows in the heat exchanger. One fluid issprayed on one side of the wall and the other is sprayed on the otherside of the wall. The intense convection that develops from either thedirect impingement and/or the evaporation for a two phase flow designallows for a very small heat exchanger to exchange a considerable amountof heat.

Referring to FIG. 7, a closed housing 12 can incorporate a dividing wall29 within the housing 12 which separates the housing 12 into two housingcompartments. In one of the housing compartments, a spray nozzle orseries of spray nozzles 36 can spray a first fluid onto one side of wall29. The first fluid can leave this housing compartment via outlet port39. One the other side of the dividing wall 29, a spray nozzle or seriesof spray nozzles 37 can spray a second fluid onto the dividing wall 29.This second fluid can leave this compartment via outlet port 38. Thefirst and second fluids can be chosen based on their properties, such asboiling point.

Heat can then be transferred between the fluids through wall 29. Theconvection heat transfer coefficient that is developed with both singlephase and two phase spray impingement is very high. This highcoefficient allows the heat exchanger to be much more compact in sizeand efficient when compared to current heat exchanger technology. Wall29 can be a flat surface or an engineered spray cooling surface such asa honeycomb or cubic chamber style surface, such as described in thesubject application. Additionally, fins or other surface extensionmechanism can be added to wall 29 to increase the effective surface areato increase the heat transfer through the wall 29.

Example 2 Spray Nozzle Expansion in Vapor Compression Cycle SprayCooling

The system described in this example can be utilized with variousembodiments of the subject invention. Specific embodiments in accordancewith the subject invention can comprise three main components: acompressor, a condenser, and a spray cooling expansion valve interfaceassembly. The cycle can begin with the compressor pulling in coolantvapor from the spray cooling assembly, and the coolant vapor beingcompressed to a temperature above ambient. The hot vapor can then flowthrough a heat exchanger to condense the vapor to liquid. The compressedhot liquid can be expanded through a nozzle and sprayed onto the spraycooling interface, or heated surface 2. Interface plate 3, as in theother embodiments of the subject invention, can be a separate plate inthermal contact with a heat source, or can be integral with a heatsource, for example, a wall of a device producing heat which needs to beremoved. A heat source, such as a laser diode or other heat exchangemedium, attached on the other side of the interface can be cooled by theexpanding and evaporating liquid. The liquid coolant can be vaporized asit removes the heat from the heat source via the interface. Inembodiments where some of the coolant is not vaporized as it departsfrom the interface, an accumulator can be inserted between the coolantdeparting the interface and the compressor in order to reduce the amountof, or prevent, liquid coolant from entering the compressor. A transferpump can be used to transfer excess liquid from the accumulator to theliquid supply line to the nozzle.

Referring to FIGS. 8 and 9, the cycle can begin with a spray coolingexpansion evaporator 10, which removes heat from a heat source 13. Theexpansion evaporator 10 can receive pressurized liquid coolant and allowthe coolant to expand between entering the nozzle and exiting thenozzle. The nozzle can also atomize the coolant as the coolant exits thenozzle and is sprayed onto the heated surface. As the liquid coolant issprayed onto the heated interface wall 45 the coolant can vaporize as itgains heat. Interface wall 45, as in the other embodiments of thesubject invention, can be a separate plate in thermal contact with aheat source, or can be integral with a heat source, for example, a wallof a device producing heat which needs to be removed. The vaporizedcoolant can flow from the expansion evaporator via connection piping 43to a compressor 20. The compressor compresses the vapor coolant to atemperature above the temperature of the condenser 30 coolant flow. Thecompressed hot vaporized coolant can flow from the compressor 20 to thecondenser 30 via connecting pipe 25. The condenser 30 can be a heatexchanger of any type designed to remove heat from a vaporized coolant,such as an ambient air to liquid heat exchanger. The pressurized hotcoolant vapor is cooled in the condenser 30 and condenses to liquid asits heat is removed. The pressurized liquid coolant can flow from thecondenser 30 via connecting pipe 24 to the spray cooling expansionevaporator 10 inlet. The expansion evaporator 10 can comprise a nozzleor a series of nozzles 40 which can spray the pressurized liquid coolanton to the heat interface wall 45. The cycle can then begin again and canrun in a continuous loop while cooling is desired.

Under some operating conditions, excess liquid can be sprayed from theimpingement nozzle 40 for enhanced heat transfer. In this case,accumulator 16, as shown in FIG. 9, may be added on line 43. Theaccumulator can retain excess liquid in line 43 from entering compressor20. Liquid coolant can accumulate in accumulator 16. A liquid pump 18can pump the excess liquid from accumulator 16 via connecting line 17 tothe liquid supply line 24 via pump discharge connecting line 19.

Example 3 Phase Separator for Spray Impingement Evaporator for VaporCompression Cycle

This example describes a phase separator 50 which can be utilized withsubject spray impingement evaporator 70 for vapor compression cycles inaccordance with the subject invention. FIG. 10A shows a specificembodiment of the subject invention that incorporates a phase separator50 in conjunction with a spray impingement evaporator 70. A sprayimpingement evaporator 70 can be added to a vapor compression cycle toimprove the heat transfer capabilities of the evaporator. The processcan begin with a compressor 20 taking in vapor from an accumulator 80.The compressed hot vapor exiting the compressor 20 goes to a condenser30 to change the phase of the vapor to liquid. The liquid can then beexpanded through an expansion valve 35. As liquid coolant is pumped fromthe accumulator 80 to the phase separator 50, the liquid in the phaseseparator 50 can be at a higher pressure than in the accumulator 80which receives vapor and liquid coolant from the impingement evaporator70 through, for example, tubing 75. The cooled liquid can then be usedin a spray impingement evaporator 70.

The addition of the phase separator 50 in this cycle in accordance withthis example can allow the process to use at least a portion of theenergy normally wasted in the expansion device to power the spraynozzles. The process enhancement can add the phase separator 50 afterthe expansion valve 35. However, in this case the pressure drop acrossthe expansion valve 35 can be small. This allows a liquid vapor mixtureat high pressure to collect in the phase separator 50. The high pressurefluid can then be used directly to power the spray nozzle in the sprayimpingement evaporator 70. Since the fluid is in both liquid and vaporphase, either a pressure atomizer or vapor atomizing nozzle can be usedin the evaporator. A transfer pump 90 may be used to transfer excessliquid from the accumulator 80 to the phase separator 50.

Referring to FIG. 10A, the process can begin with a coolant vaporflowing from an accumulator 80 via compressor intake line 14 to thecompressor 20. The vaporized coolant can be pressurized causing thetemperature to rise. The hot coolant vapor can flow from the compressor20 to the condenser 30 via connection line 15. The condenser 30 is aheat exchanger designed to remove heat from the hot vapor causing it tochange phase to liquid. Condenser 30 can be any type of heat exchangingdevice, such as an air to liquid style allowing the heat to be pumpedinto ambient air, or any other medium that is at a colder temperaturethan the condensing temperature of the coolant. The compressed liquidcoolant can flow from the condenser 30 to the expansion device 35 viaconnecting line 22. The expansion of the compressed liquid coolant cancause it to vaporize and cool. The mixed phase coolant can flow from theexpansion device 35 via connecting line 26 to the phase separator 50.The expansion permitted in the expansion device 35 can be limited ascompared to a conventional vapor compression cycle so that the pressurewithin the phase separator 50 is higher than the pressure in theaccumulator 80. As liquid coolant is pumped from the accumulator 80 tothe phase separator 50, the liquid in the phase separator can be at ahigher pressure than in the accumulator 80 which receives vapor andliquid coolant from the impingement evaporator 70 through, for example,tubing 75.

The phase separator 50 can separate the phases to liquid and vapor. Thephase separator 50 and accumulator 80 rely on the densities of thefluids within them and gravity to separate the fluids into vapor andliquid phases. A typical design can be a cylindrical, spherical, or boxshape. Both components have an inlet port that flow both liquid andvapor. The outlets ports are then positioned so that individual phasesleave the component. The spray cooling cycle, for example as shown inFIGS. 10A, 10B, and 13, may have applications, such as spaceapplications, where gravity is low or not available. For zero gravity orlow gravity applications, a separating force can be applied to theinternal fluids to separate the phases. Such forces can be, for example,centrifugal such as those produced by a rotating drum.

The liquid coolant can flow from the bottom of the phase separator 50via connecting line 55 to the spray nozzle liquid inlet port in thespray impingement evaporator 70. The spray impingement evaporator 70 canincorporate an interface plate 3 as discussed with respect to FIG. 1 andothers. Interface plate 3, as in the other embodiments of the subjectinvention, can be a separate plate in thermal contact with a heatsource, or can be integral with a heat source, for example, a wall of adevice producing heat which needs to be removed. The vapor coolant fromthe phase separator 50 can flow via vapor connecting line 60 to eitherthe vapor inlet port of the spray nozzle or directly to the accumulator80 depending on the type of nozzle used in the spray impingementevaporator 70. The liquid coolant gains heat in the evaporator 70 andvaporizes. The vaporized coolant and excess liquid can flow from thespray impingement evaporator 70, via connecting line 75, to theaccumulator 80. A transfer pump 90 may be added to the cycle to transferexcess liquid from the accumulator 80 via connecting line 85 to thephase separator 50 via connecting pipe 95.

Referring to FIG. 10A, but not limited to the embodiment shown in FIG.10A, spray impingement evaporator 70 is shown connected to the vaporcompression cycle via lines 55, 60, and 75. In this way the spraying andvapor compression functions can be geographically separated. This canallow a smaller housing for spray impingement evaporator 70 which takesup less space and can be more conveniently brought into contact withheat sources where space can be a premium. In addition, a plurality ofspray impingement evaporators 70 can be connected to a single vaporcompression cycle system through a corresponding plurality of linescorresponding to lines 55, 60, and 75. The physical separation of thespraying and vapor compression functions can be accomplished in theother embodiments described in the subject application. Again, sprayimpingement evaporator 70 can utilize one of a variety of nozzle typesas described in the subject application. Also, as other embodimentsdescribed in the subject application utilized an essentiallygravity-based phase separator, the phase separator 50 shown in FIG. 10Acould also be utilized with these embodiments.

In the embodiment shown FIG. 10B, compared with the embodiment shown inFIG. 10A, the accumulator 80 and transfer pump 90 have been removed fromthe embodiment shown in FIG. 10A. As a result, the coolant in tube 75connects directly to tube 14 and is transported to the compressor 20. Inan embodiment where compressor 20 is a style of compressor that can onlyexcept vapor at its inlet, then the coolant in tube 14 can be all vapor.In such an embodiment, if any liquid remains in tube 75 as a result ofthe spray cooling process, then this liquid can be vaporized beforeentering the compressor. In another embodiment where less than all thespray cooling liquid is vaporized in the spray cooling process, and ameans to vaporize the remaining liquid in tube 75 is not desired, acompressor 20 that can except a portion of liquid at its inlet can beused.

Example 4 Surface Area Enhancement for Heat Transfer Surfaces

The subject invention also relates to a heat transfer apparatus havingan enhanced surface which can increase the rate of heat transfer fromthe surface to an impinging fluid. The subject enhanced surface can beincorporated with any of the heat transferred surfaces disclosed in thesubject patent application or incorporated with other heat transfersurfaces. The subject invention also pertains to heat transferapparatus, such as heat transfer plates, which incorporate the subjectenhanced surfaces. The subject enhanced surfaces can also be utilizedfor heat desorption from a surface.

In a specific embodiment, the subject system can comprise: a housing, afluid pump or compressor, a nozzle array consisting of one or morenozzles, and a high heat flux source interface plate. The process beginswith the housing. The housing contains the working fluid. The process asshown in FIG. 11 begins with the entire assembly placed within a housing340. The housing is then filled with the desired coolant to a levelwhich allows an adequate pumping reservoir 345 without impending on thecoolant flow. A pump or compressor draws the coolant from the housingand pressurizes it. The pressurized coolant is forced through the nozzlearray. The nozzles atomize the coolant onto the heated surface to removeheat from the heat source 364. The surface is enhanced to increase theeffective cooling area of the spray.

Evaporative spray cooling is enhanced by maintaining the thinnest liquidlayer possible on the heat transfer surface. Pressure atomizer nozzlesuse high pressure liquid and vapor atomizer nozzles use compressed vaporto atomize the liquid coolant. Both types of nozzles can be used toproduce a high velocity and lower droplet density spray. The result is aspray of liquid coolant onto the extended surface area which takesadvantage of the additional surface area.

The pump 346 draws in the liquid coolant and pressurizes it to thedesired pressure. The pressurized liquid goes to the liquid inlet portof spray nozzle 353. Compressor 350 draws in coolant vapor andpressurizes it to the desired pressure. The pressurized coolant vapor issent to the vapor inlet port 343 on spray nozzle 353. The compressedvapor and the pressurized liquid coolant combine in nozzle 353 to formsmall liquid droplets with a high velocity.

The spray nozzle 353 can be a vapor atomizer nozzle as shown using bothcompressed vapor and liquid coolant or a pressure atomizer nozzle, notshown, which uses only pressurized liquid.

The droplets impinge on cooling plate 360. Multiple surface areaenhancements 370 are connected to cooling plate 360 as shown in FIGS.12A-12E. The enhancements can be milled into or extend from the surfaceor can be thermally attached to the surface 360. The enhancements can beprotrusions from surface 360 as shown in FIG. 12A or indentations intosurface 360 as shown in FIG. 12B. The enhancements can be of any shapeincluding but not limited to rods, cubes, cones, or pyramids. FIGS.12A-12E show variations of possible surface enhancements that improvespray cooling. However, any geometric shape or combination of shapesintruded into and extended from the surface can be used as surfaceenhancements. The subject protrusions and/or indentations can be createdby, for example, sandblasting the surface. In addition, the subjectenhanced surfaces with protrusions and/or indentations can also besandblasted to increase the heat transfer properties of the surface.

In a specific embodiment, protrusions, and/or indentations, having aheight and/or depth, to diameter ratio of between about 0 to about 10can be utilized. In further specific embodiments, a height, and/ordepth, to diameter ratio of between about 1 and about 5 can be utilized.In another embodiment, protrusions, and/or indentations, having a heightto spacing between adjacent protrusions, and/or indentations, ratio ofbetween about 2 and 4 can be utilized. In a further embodiment, aheight, and/or depth, to diameter ratio of about 3 can be utilized. In aspecific embodiment, the number of protrusions, and/or indentations,density/spray cooling area is between about 1 and about 100 per squarecentimeter. In a farther specific embodiment, the number of protrusions,and/or indentations, density/spray cooling area is between about 10 andabout 20 per square centimeter. In a specific embodiment, the subjectsurface enhancements can increase the surface area, as compared to asmooth surface, by about 1 to about 5 times. In a further specificembodiment, the subject surface enhancements can increase the surfacearea by about 1.1 to about 2. In a specific embodiment, the center tocenter spacing of the subject protrusions, and/or indentations isbetween about (0.1) d and about 10d, where d is the diameter (or meandiameter) of the protrusions, and/or indentations. In a further specificembodiment, the center to center spacing is about d. In a specificembodiment, the roughness of the subject enhanced surface can have a RMSof between about optically smooth and about 100 micrometers.

The vapor coolant can then flow to a condenser, such as coil 342. Thevapor condenses on the condenser coil 342 and forms liquid. The liquidthen flows into reservoir 345. A heat extractor 341 removes the heatfrom the condenser 342 via thermal connection. The heat extraction canbe a refrigeration cycle or an ambient heat exchanger.

A series of control devices including thermocouples, flow meters andlevel indicators are used to control the process in order to maintainthe desired operating conditions.

The cycles shown in FIGS. 6, 8, 9, 10A, 10B, and 13 can utilize controlfeatures to maintain operating conditions. For spray cooling,maintaining a constant temperature of the cooled device can beimportant. Therefore, the control system can monitor the conditionswithin the cycle and make the proper adjustments.

The control system can be an active electronic system usingelectronically actuated valves and temperature and pressure sensors. Acomputer operated device, such as a Programmable Logic Controller canmonitor the sensors and make adjustments to the control valves tomaintain conditions. In addition, the control system can utilize smartvalves that mechanically monitor the cycle conditions and change portsettings due to mechanical or thermal forces. The control system canalso utilize a combination of both mechanically activated andelectronically activated valves.

Example 5 Thermal Energy Storage Unit

The subject invention can incorporate thermal energy storage devicedesigned to collect thermal energy when energy is present and store itfor use or dissipation at a later time. The subject invention canutilize a thermal energy storage device which relies on sensible heattransfer and storage and/or latent heat transfer and storage. Thetemperature of the storage media can vary depending on the type ofstorage used. For the purpose of spray cooling, latent heat storage thatproduces a near constant temperature is the most practical. However,sensible heat storage can also be used. The use of thermal energystorage permits the removal of heat energy from the condenser in a vaporcompression cycle without requiring high pressure hot vapor. This is aparticular benefit when spray cooling is adapted to high energy laserthat have a short cycle time. Since it is preferable for high energyelectronics to be cooled in real time, the thermal management systempreferably removes the heat in real time. If the system is continuousduty, the heat dissipation from the cooling cycle should match the heatgeneration. However, if the heat generation occurs over short bursts,the heat dissipation can be sized to the average heat generation,provided a thermal energy storage device is available to store the peakloading.

In specific embodiments of the subject invention the condenser, shown as31 in FIG. 6 and 30 in FIGS. 8, 9, 10A, and 10B, can be replaced with athermal energy storage unit. FIG. 13 shows an embodiment of the subjectinvention using thermal energy storage 42 rather than a standardcondenser.

The cycle presented in FIG. 13 takes full advantage of a thermal energystorage (TES) unit 42. As long as the TES is lower in temperature thanthe spray cooling liquid, vapor will flow via connection tube 44 to theTES unit 42. Since the temperature inside the TES is lower, the vaporwill condense to liquid. The expansion valve 35 in FIG. 10A is replacedwith a small pump 41 in FIG. 13 to pump the liquid from the TES 42 tothe phase separator 50. Since high temperature compressed vapor is nolonger needed for condensing in a standard vapor compression cyclecondenser, the compressor's only purpose is to produce cool, lowpressure vapor for the nozzles. Therefore, compressor 20 draws in coolvapor from connection tube 44 and compresses it slightly. The slightlycompressed vapor then ports to phase separator 50. The compressor 20 canalso port directly to the vapor inlet port of the spray nozzles. In aspecific embodiment, the compressor 20 increases the pressure of thevapor by 5 to 20 psi.

The subject invention relates to a closed cycle spray cooling loop. Thesubject spray cooling cycle cools a heat source and rejects that heatfrom the cycle. The cycle can be configured using to accomplish one ormore of the following: 1. spraying coolant onto a surface to be cooled;2. pumping the coolant through the flow loop; 3. rejecting heat from theclosed loop; and 4. re-condensing the evaporated coolant. The particulararrangement of the components and the specific embodiment of eachcomponent can vary depending on the application and requirements of thesystem. In addition, other optional components may be added. Suchoptional components can accomplish, for example, one or more of thefollowing: 5. phase separation of liquid and vapor; 6.expansion/diffusion of high pressure coolant; and 7. sub-cooling ofinput liquid to spray nozzle.

An embodiment of the subject invention can incorporate a means forspraying the coolant onto a surface to be cooled. A spray nozzle can beutilized, where the spray nozzle can be a single nozzle or an array ofnozzles. Examples of such spray nozzles are shown in FIGS. 1-4. Thenozzle can be, for example, a pressure atomizer nozzle, a vapor assistnozzle, or a two phase flow nozzle. A two phase flow nozzle is one thatcan input a mixed flow. The inlet to the nozzle may be liquid, separatedvapor and liquid flows, or two phase flow. If a pressure atomizer nozzleis used the coolant inputted to the nozzle is preferably a pure singlephase liquid. An embodiment that can incorporate a pressure atomizernozzle is shown in FIG. 5, where single phase liquid can flow throughthe tube connecting the pump 8 and pressure atomizing nozzle 5. As isshown in FIG. 5, a single tube can transport liquid coolant to thenozzle 5. If a vapor assist nozzle is used, the coolant inputted intothe nozzle 5 is preferably both single phase liquid and single phasegas, preferably transported in separate tubes. An embodiment that canincorporate a vapor assist nozzle is shown in FIG. 10A, where singlephase liquid can flow through tube 55 and single phase can vapor flowthrough tube 60 to the vapor assist nozzle in the expansion evaporator70. An embodiment that can incorporate a two phase nozzle is shown inFIG. 8. A single tube can transport a mix of liquid and vapor in tube 24to the nozzle 40. The coolant sprayed onto the surface acquires the heatat the surface 13 resulting in two phase spray cooling heat transfer.

An embodiment of the subject invention can incorporate a means to pumpthe coolant. A pump can be used for this purpose, where a pump is anytype which can move liquid and/or vapor, either together or separately.Examples of a liquid pump include, but are not limited to, a rotary vanepump, a gear pump, and a piston pump. Examples of vapor pumps include,but are not limited to, a piston pump, a centrifugal pump, and a Wankelcompressor. Examples of mixed flow pumps include, but are not limitedto, a diaphragm pump, and a positive displacement pump. Numerous typesof pumps are known to those skilled in the art can be used, depending onthe coolant liquid/vapor phase and depending on the configuration of thecycle. In an embodiment utilizing a two phase nozzle, a two phase pumpmay be used. An example of this is shown in FIG. 8 where compressor 20can be a two phase pump, where two phase flow enters from the exit ofthe nozzle through 43 and exits the pump 20 as two phase through line25. If a vapor assist nozzle is used then both a compressor and pump canbe used. An embodiment that can use a combined pump and compressor topower the flow of the cycle is shown in FIG. 10A. In this embodiment,liquid pump 90 and vapor compressor 20 work together to pressurize theinlets 55 and 60 to the nozzle 70. A cycle may also use a compressoralone as in FIG. 10B where the compressor 20 pressurizes vapor that iscondensed and expanded to provide pressurized vapor and liquid to thenozzle 70.

An embodiment can utilize a means to reject heat. Any heat exchangerthat interfaces with a heat sink can be utilized. An example of such aheat exchanger is shown in FIG. 5, where heat is removed from theworking fluid with heat exchanger 54. Heat can be rejected to a heatsink that operates at a colder temperature than the working fluid.

An embodiment can utilize a means to re-condense the evaporated liquid.Any condenser can be utilized. Most commonly the heat rejection andcondensation process is simultaneous. An example of this is shown inFIG. 9 where vapor enters the condenser 30 through 25 and exits as aliquid through line 24. While traveling through the condenser heat isrejected from the cycle to a heat sink. Condensation can also be done bysub-cooled spray in a saturated vapor environment as shown by 56 in FIG.5.

An embodiment can utilize phase separation. A phase separator oraccumulator can be utilized for phase separation. A phase separator canbe used at any point in the cycle when a mixed flow of liquid and vaporneed to be separated into distinct individual flows to accommodate thenext device in the flow loop. An example is shown in FIG. 10A, where thephase separator 50 has inputs of two phase and liquid through lines 26and 95, respectively. The phase separator then outputs separated liquidand vapor flows to the nozzle through lines 55 and 60, respectively.Another example is also shown in FIG. 10A, when the mixed flow in tube75 is separated into individual flows of liquid and vapor to accommodatethe choice of selecting a liquid pump and a vapor pump that can onlymove liquid and vapor, not a mixed flow. However, if a single mixed flowpump is selected, as shown in FIG. 8, then a phase separator is notneeded. The phase separator and accumulator can rely on the densities ofthe fluids within them and gravity to separate the fluids into vapor andliquid phases. A typical design can be a cylindrical, spherical, or boxshape. Both components have an inlet port that flow both liquid andvapor. The outlet ports are then positioned so that individual phasesleave the component. The spray cooling cycle, for example as shown inFIG. 10A may have applications, such as space applications, wheregravity is low or not available. For zero gravity or low gravityapplications, a separation force can be applied to the internal fluidsto separate the phases. Such forces can be, for example, centrifugalsuch as those produced by a rotation drum.

An embodiment can utilize expansion/diffusion. A valve can be used forexpansion/diffusion. Expansion of a saturated liquid typically producessome vapor, creating a two phase flow. An example of an expansion valveis shown in FIG. 10A as 35 where single phase liquid exits the condenser30 through line 22 at a high pressure. The expansion valve 35 lowers thepressure to the desired inlet conditions of the nozzle evaporator 70. Anexpansion valve 35 is used to allow the condenser 30 to operate athigher pressure than the spray process requires. This strategy allowsadaptation to higher temperature heat sinks; by increasing the pressureof the working fluid, the temperature is also increased. In this way,the temperature can be increased above the heat sink more easily.

An embodiment can utilize sub-cooling input liquid to the nozzle. A heatexchanger that can transfer heat and maintain separation of two flowscan be used for sub-cooling input liquid to the nozzle. Sub-cooling ofthe input liquid coolant to the nozzle can be accomplished using thecold two phase flow exiting the nozzle. This can be used to help preventboiling and/or re-condense any liquid that did boil while transferringto the nozzle. An embodiment utilizing this technique is diagramed inFIG. 31 where the input vapor 569 enters a nozzle 564 directly, and theinput liquid 567 enters a heat exchanger 565 and either condensesbubbles which were flowing or cools the liquid to prevent any bubbles.This can ensure that the tube 568 will carry single phase liquid to thenozzle 564. The heat is transferred to the two phase flow 566 exitingthe nozzle. Since the two phase flow is saturated it will typicallyincrease in quality as it flows through the heat exchanger 565. Unlessall the liquid is evaporated, the temperature of the exhaust flow 566will remain constant throughout the heat exchanger 565.

The cycle shown in FIG. 5, incorporates a phase separator component,which is needed because the exhaust of the nozzle is two phase.Therefore, liquid is separated from the vapor and sent to the pump. Thesubject invention relates to a variety of combinations of componentorder and configuration so that many different cycle variations may beachieved.

Condenser Configurations

Spray cooling can capitalize on the benefits of phase change heatremoval such that the spray cooling cycle has a mix of vapor and liquidat some point in the cycle. The ratio of vapor mass to the total flowmass flowing through a tube can be defined as the quality of the twophase flow. For example, a low quality (high concentration of liquid)flow can enter a two phase nozzle and exit from the sprayed surface ahigh quality flow (high concentration of vapor) due to liquid coolantevaporation in the nozzle. The evaporated liquid is what caries the heatthat was acquired from the surface. In other words, re-condensing theevaporated liquid will reject the acquired heat. Therefore, a condenserserves to reject the proper amount of heat by condensing the evaporatedliquid and, preferably, all of the evaporated liquid.

A condenser can condense the evaporated liquid and reject the acquiredheat in several different fashions, examples of which are described asfollows:

The condenser may accept all of the exhaust flow as two phase and thenre-condense the evaporated liquid, leaving two phase to exhaust in thecase of a two phase nozzle application, or single phase liquid in thecase of a pressure atomizing nozzle. This function of the condenser canbe used in embodiments shown in FIGS. 8, 10B (with expansion valve 35removed), 15, 18, 19, and 28. In FIG. 8, in a specific embodiment, theexhaust of the nozzle 40 will flow as a high quality two phase flowthrough 43 to the two phase pump 20 and then to the condenser 30 through25 still as a two phase flow. The exhaust of the condenser through line24 then will be two phase. If a pressure atomizing nozzle is used thencondensing all of the evaporated liquid will provide for single phaseliquid exhausting the condenser through line 24. In FIG. 18, in aspecific embodiment, exhaust from nozzle 425 enters condenser 427 vialine 426 and exits as two phase flow to compressor 429 via line 428. Theexhaust of the compressor 429 is still two phase as it enters a phaseseparator 431 via line 430. Separated vapor and liquid enters the nozzle425 via lines 432 and 433, respectively.

An expansion valve may be used to allow the condenser to operate at ahigh pressure. High pressure condensers can reject heat to highertemperature heat sinks which is helpful if a cold heat sink is notavailable for the application. When placing an expansion valve after thecondenser, the condenser may re-condense all of the vapor in the twophase flow, not just the evaporated coolant. Vapor required for a twophase or vapor-assist nozzle will be regained when the flowing coolantexpands through the valve, lowering the pressure of the coolant by whichsome evaporation will produce the proper amount of vapor flow requiredfor the nozzle. The same FIGS. 8, 10B, 15, 18, 19, and 28 can be used torepresent the condenser function, providing that the condenser/expansionvalve exist as a single unit in the figures (except FIG. 10B where theexpansion valve 35 is already diagramed separately). FIG. 30 is used tobetter show the condenser/expansion valve as a single unit. When asingle component condenser is drawn as is 557 it may represent the casewhere a condenser 560 and an expansion valve 561 are in line. In eithercase a two phase flow or single phase vapor will enter in 556 or 559 andexit as a two phase flow through 558 and 562. In FIG. 8, for a specificembodiment example, the condenser 30 can condense the two phase flowthat entered through line 25 to a single phase liquid at a highpressure. The flow can then be expanded to a lower pressure and exit asa two phase flow to line 24. For this specific embodiment, the nozzle 40is a two phase nozzle.

The condenser may accept only vapor from the nozzle exhaust and bypassthe liquid flow. In this case, a phase separator can be used upstream tosend the single phase vapor to the condenser. The vapor flow then wouldinclude the evaporated liquid and the original vapor sent to the nozzle,if using a vapor assist nozzle. The condenser therefore only condensesthe evaporated liquid, leaving the original vapor flow as is. Therefore,the exit of the condenser will still have two phase flow at the exit.The bypassed liquid will need to be combined with the newly condensedliquid before entering the nozzle. This function of the condenser can beused in cycle examples displayed in FIGS. 9, 10A, 20, and 25. In FIG. 9,for a specific embodiment, the entrance to the condenser 30 flows singlephase vapor through 25. The exit of the condenser flows two phase flowthrough 24.

An expansion valve may be used in this configuration as well. Whenplacing an expansion valve after the condenser, the condenser mayre-condense all of the vapor of the inlet flow, not just the portion ofthe vapor that is the evaporated coolant. Vapor required for a two phaseor vapor-assist nozzle will be regained when the flowing coolant expandsthrough the valve, lowering the pressure of the coolant by which someevaporation will produce the proper amount of vapor flow required forthe nozzle. This function of the condenser can be used in cycle examplesalso displayed in FIGS. 9, 10A, 20, and 25, providing that thecondenser/expansion valve exist as a single unit in the figures (exceptFIG. 10A where the expansion valve 35 is already diagramed separately).In FIG. 9, in a specific embodiment, the condenser 30 can condense thesingle phase vapor flow that entered through line 25 to a single phaseliquid at a high pressure. The flow can then be expanded to a lowerpressure and exit as a two phase flow to line 24. For this specificembodiment, the nozzle 40 must be a two phase nozzle.

The condenser can also accept only the vapor from the evaporated liquid,bypassing the other exhaust (liquid and vapor) from the nozzle. A phaseseparator would be preferred for this type of condenser as well. Thiscondensation process will typically have a lower amount of mass flowingthrough it compared with condenser configuration described above. Thisfunction of the condenser can be used in cycle examples shown in FIGS.13, 17, 23, 26, and 29. In FIG. 17, for a specific embodiment example,the single phase vapor enters the condenser 422 and exits as a singlephase liquid through 424.

Coolant Pumping

Two phase pumps typically move high ratios of liquid to vapor. Higherratios of liquid to vapor can exist after the condenser and before thenozzle evaporator. It is possible to push vapor through a condenser witha compressor so that liquid exits. It is also possible to suck liquidout of the condenser using a pump. Therefore placing a compressor beforethe condenser or a pump after would have the same result. Both acompressor and a pump can be placed inline with a condenser betweenthem, where each does half the work.

Heat Rejection Condenser and Pump Arrangements

Two Phase Arrangements

If no phase separator is placed after the nozzle evaporator then a twophase pump and two phase condenser can be used. Configuring the order ofthe components can be decided based on the advantages and disadvantagesof pumps and condensers discussed above. Cycles with the condenserplaced before the two phase pump are shown in FIGS. 15 and 18. In FIG.15, for a specific embodiment example, the condenser is placed directlyafter the nozzle component. With no phase separator in-between, thecondenser 402 will receive two phase flow from 401. The two phase pump404 is placed after the condenser and receives low quality flow which ispressurized and sent to the nozzle array. The cycle may also use apressure atomizing nozzle as 400. In this case all of the evaporatedliquid will be condensed in 402 and exit as a single phase liquid at403. Therefore a single phase liquid pump 404 would pressurize thecoolant and send single phase liquid through 405 to the nozzle. Bothcycles of FIGS. 15 and 18 can use the optional expansion valve 561 toincrease the condenser pressure. Furthermore, since the cycle of FIG. 18sends separated vapor and liquid flow to the nozzle, a sub-cooler may beadded to the cycle.

Cycles with the two phase pump placed before the condenser are shown inFIGS. 8 and 10B. In FIG. 8, for a specific embodiment example, two phaseflow exits the nozzle array through 43 and enters the two phase pump 20at a high quality. The pressurized flow then enters the condenser 30through line 25 and exits as a low quality flow through line 24 tore-enter the nozzle array 40. This specific cycle may also use apressure atomizer nozzle in place of expansion evaporator 10. In thiscase the condenser 30 would condense all of the evaporated liquidleaving a single phase liquid to exit and flow to the pressure atomizingnozzle. Both cycles of FIGS. 8 and 10B can use the optional expansionvalve 561 to increase the condenser pressure. Furthermore, since thecycle of FIG. 10B sends separated vapor and liquid flow to the nozzle, asub-cooler may be added to the cycle.

Separated Flow Arrangements

If a phase separator is placed after the nozzle array then a separatedflow arrangement can be made. In this case a separate vapor compressorand liquid pump can be used to move the coolant. As shown for the twophase arrangements, two variations exist where the placement of thefluid pumping and heat rejection condenser can be switched. Cycleexamples where the condenser or thermal energy storage unit is placedbefore the liquid pump are shown in FIGS. 13 and 21. In FIG. 13, for aspecific embodiment example, the exhaust flow 75 of the nozzle enters aphase separator 80 first. Some vapor flow then moves to the TES 42 vialine 44 and fully condenses to single phase liquid at line 22 where itcan combine with the bypassed liquid 85. The single phase liquid at line22 and the bypassed liquid 85 can enter an optional phase separator 50through pumps 41 and 90, respectively, and then can travel to the nozzlearray 70. Some vapor flow can enter the compressor 20. Once compressed,the flow can enter an optional phase separator 50 and then travel to thenozzle array 70. FIG. 21 shows the same cycle arrangement with theelimination of the optional phase separator 50. The exhaust flow 454 ofthe nozzle 453 enters a phase separator 455. Then some vapor flow 456moves to the condenser 458 and some vapor flow 457 moves to a vaporcompressor 463 that sends vapor flow 464 to the nozzle 453. Thecondenser 458 fully condenses the vapor flow 456 to a single phaseliquid flow 460, which then combines with the liquid flow 459 leavingthe phase separator 455. The combined liquid flows 459 and 460 enter aliquid pump 461 and then travel to the nozzle 453 via line 462. Becausethe liquid entrance flow of the nozzle is in an independent line, a heatexchanger may be used to sub-cool the liquid as shown in FIG. 31.

Cycle examples where the compressor is placed before the condenser areshown in FIGS. 23 and 26. In FIG. 23, for a specific embodiment example,the exhaust flow 477 of the nozzle 476 enters a phase separator 478first. Separated liquid and vapor flows 479 and 398 enter a pump 480 andcompressor 482 respectively. Part of the pressurized vapor flow 483enters a condenser 485 where it is fully condensed. The two liquid flows486 and 481 combine and enter nozzle 476, and separate vapor 484 entersthe nozzle 476 via line 484. FIG. 26 shows the same cycle arrangementwith the addition of a phase separator 528 in liquid line 486 afterliquid flow 481 combines with the liquid flow exiting the condenser 485and vapor line 484 such that liquid flow enters nozzle 476 via line 526and vapor flow enters nozzle 476 via line 527. Because the liquidentrance flow of the nozzle is in an independent line, a heat exchangermay be used to sub-cool the liquid as shown in FIG. 31.

Separated Flow Entrance with “Single Phase Inlet and Two Phase Outlet”Condenser

If a phase separator is placed after the nozzle array then the entranceto the condenser and fluid pump will exist as separated components. Inthis case if the condenser is configured to accept all of the vapor flowthen a two phase pump will be required. Cycle examples of thisconfiguration are shown in FIGS. 20 and 25. In FIG. 20, for a specificembodiment example, two phase flow 446 enters the phase separator 447first. All of the vapor 448 enters the condenser 449 and exits as twophase or as single phase liquid through 451 if a pressure atomizernozzle is used. The bypassed liquid 450 is then combined with the twophase or single phase liquid flow 451 of the condenser and they enter atwo phase pump or single phase liquid pump 452. Pressurized two phase orsingle phase liquid flow then enters the two phase or pressure atomizingnozzle 445. For a specific embodiment example, as shown in FIG. 25, allof the vapor 488 enters the condenser 449 and exits as two phase liquidthrough 451. The bypassed liquid 450 does not combine with the two phaseflow 451. Instead, the bypassed liquid 450 moves through liquid pump 509and into a second phase separator 512 via line 510. The two phase flow451 enters a two phase liquid pump 452 and then enters the second phaseseparator 512 via line 511. Vapor flow and liquid flow enter nozzle 501from the second phase separator 512 via lines 513 and 514, respectively.Both cycles of FIGS. 20 and 25 can use the optional expansion valve toincrease the condenser pressure. Furthermore, since the cycle of FIG. 25sends separated vapor and liquid flow to the nozzle, a sub-cooler may beadded to the cycle.

Switching the order of the condenser and fluid pump will allow the useof single phase pumps. Cycle examples of this configuration are shown inFIGS. 9 and 10A. In FIG. 9, for a specific embodiment example, all ofthe vapor that is separated in the phase separator 16 is compressed incompressor 20 and sent through the condenser 30. This flow then exitsthe condenser 30 as two phase flow through line 24 after all of theevaporated liquid from the nozzle array has been condensed. The liquidflow from the phase separator 16 is sent to a pump 18 via line 17 and iscombined with the two phase flow exiting the condenser before it entersthe nozzle array. This cycle may also use a pressure atomizing nozzleand flow single phase liquid out of the condenser. Both cycles of FIGS.9 and 10A can use the optional expansion valve to increase the condenserpressure. Furthermore, since the cycle of FIG. 10A sends separated vaporand liquid flow to the nozzle, a sub-cooler may be added to the cycle.

Separated Flow Entrance with “Two Phase Inlet and Single Phase Outlet”Condenser

In an embodiment, the condenser can condense two phase flow to a singlephase liquid flow. Cycle examples of this configuration are shown inFIGS. 22 and 24. In FIG. 22, for a specific embodiment example, twophase exhaust 466 enters phase separator 467 first. A two phase flowenters the condenser 469 from the phase separator 467 via line 468.Single phase liquid flow leaves the condenser 469 through line 470 andis sent through pump 471 to the nozzle 465 via line 472. The vapor flowexits phase separator 467 through line 473 and is sent through vaporcompressor 475 before it enters the nozzle array 465 via line 474. FIG.24 shows the same cycle arrangement with the addition of a phaseseparator 498 in liquid flow line 472 and vapor flow line 474 such thatsingle phase liquid exits phase separator 498 and enters nozzle 465 vialine 500 and vapor flow exits phase separator 498 and enters nozzle 465via line 499.

Phase Separation Between Condensing and Pumping

If no phase separator exists after the nozzle component, then the twophase flow can enter either the condenser or a two phase pump. If thecondenser is placed first, then the flow will enter two phase of a highquality and exit as a low quality. The two phase flow can then enter aphase separator and then enter a pump and compressor, sent as separatedflows to the nozzle component. This cycle arrangement is shown in FIGS.19 and 28. In FIG. 19, as a specific embodiment example, two phase flowfrom the nozzle exhaust 435 enters the condenser 436 first. Flow thenexits via line 437 at a lower quality and enters a phase separator 438.Vapor flow is sent to a vapor compressor 442 before entering nozzlearray 434 via line 444 and liquid flow is sent to a liquid pump 441before entering nozzle 434 via line 443. The vapor compressor 442 andliquid pump 441 are used to increase the pressure of the vapor flow inline 439 and liquid flow in line 440 before the nozzle array 434. Bothcycles of FIGS. 19 and 28 can use the optional expansion valve toincrease the condenser pressure. FIG. 28 shows the same cyclearrangement as FIG. 22 with the addition of a second phase separator 541in liquid flow line 443 and vapor flow line 444 such that vapor flowenters nozzle 434 via line 542 and liquid flow enters nozzle 434 vialine 543. Because the liquid entrance flow of the nozzle is in anindependent line, a heat exchanger may be used to sub-cool the liquid asshown in FIG. 31.

Alternatively, a two phase pump can be used to increase the pressurefirst, to then send the two phase flow to a phase separator. If acondenser is used that excepts all of the vapor flow and exhausts twophase flow, then bypassed liquid and the two phase outlet of thecondenser will have to be combined and sent to either a phase separatoror a two phase nozzle. Cycle examples of this arrangement are shown inFIGS. 16 and 27. In FIG. 16, for a specific embodiment example, exhaustflow 407 enters a two phase pump 408 first. The mixed flow 409 is thenseparated in a phase separator 410. The vapor flow 411 is then sent to acondenser 413 and exits as two phase flow 399. The liquid flow 412 iscombined with the two phase flow 399 and then sent to a two phase nozzle406. This cycle can also be configured for a pressure atomizing nozzlewhere single phase liquid exits the condenser 413. In FIG. 27, for aspecific embodiment example, the vapor flow 411 is sent to condenser 413and exits as a two phase flow via line 536. The two phase flow 536enters a second phase separator 537. The liquid flow 412 is sentdirectly to the second phase separator 537. Then, vapor flow is sentfrom the phase separator 537 to the nozzle 529 via line 538 and liquidflow is sent to the nozzle 529 via line 539. Both cycles of FIGS. 16 and27 can use the optional expansion valve to increase the condenserpressure.

If a condenser is configured to have a single phase inlet and outletthen the separated liquid and vapor flow is available to send to a vaporassist nozzle. Cycle examples of this configuration are shown in FIGS.17 and 29. In FIG. 17, for a specific embodiment example, the exhaust415 of the nozzle 414 enters a two phase pump 416 and then enters aphase separator 418 via line 417. Part of the vapor is sent to thecondenser 422 via line 419 where it is fully condensed. This liquid iscombined with the liquid 423 of the phase separator 418. Separatedliquid via line 424 and vapor via line 420 is then sent to a vaporassist nozzle 414. In FIG. 29, for a specific embodiment example, twophase exhaust from nozzle 44 enters a vapor compressor 546 via line 415.Two phase flow exits vapor compressor 546 and enters the phase separator418 via line 417. Part of the vapor is sent to condenser 422 where it isfully condensed. This liquid combines with the liquid 423 of the phaseseparator 418 and enters a second phase separator 548 via line 555. Theother part of the vapor from phase separator 418 is sent to the secondphase separator 548 via line 554. Vapor and liquid is sent to nozzle 414from the second phase separator 548 via lines 549 and 550, respectively.Both cycles of FIGS. 17 and 29 can use the optional expansion valve toincrease the condenser pressure. Because the liquid entrance flow of thenozzle is in an independent line, a heat exchanger may be used tosub-cool the liquid as shown in FIG. 31.

All patents, patent applications, provisional applications, andpublications referred to or cited herein are incorporated by referencein their entirety, including all figures and tables, to the extent theyare not inconsistent with the explicit teachings of this specification

Sample and embodiments described herein are for illustrative purposesonly and that various modifications or changes in light thereof will besuggested to persons skilled in the art and are to be included withinthe spirit and purview of this application and the scope of the appendedclaims.

1. A method of removing heat from a heat source, comprising: locating apiece of material having a plurality of subsections, wherein eachsubsection shares a partition wall with at least one adjacent subsectionin contact with a surface of a heat source; and spraying a liquidcoolant through each subsection onto the surface of the heat source,wherein the liquid coolant sprayed onto the surface of the heat sourceabsorbs heat from the surface of the heat source, and carries theabsorbed heat away as the coolant leaves the surface of the heat source,wherein the partition wall shared by a subsection with an adjacentsubsection reduces the flow of coolant from the subsection to theadjacent subjection and the flow of coolant from the adjacent subsectionto the subsection.
 2. The method according to claim 1, furthercomprising; creating a seal between the partition walls and the surfaceof the heat source.
 3. The method according to claim 1, wherein the heatsource is a power electronic device.
 4. The method according to claim 1,wherein spraying a liquid coolant onto the surface of the heat sourcecomprises spraying an atomized liquid coolant onto the surface of theheat source.
 5. The method according to claim 4, wherein spraying anatomized liquid coolant onto the surface of the heat source comprisesspraying droplets having mean diameters in a range from about 10 micronsto about 200 microns and velocities in a range from about 5 meters persecond to about 50 meters per second.
 6. The method according to claim4, wherein spraying an atomized liquid coolant onto the surface of theheat source comprises spraying droplets having a size and velocity suchthat the effects of gravity are negligible.
 7. The method according toclaim 4, wherein spraying an atomized liquid coolant onto the surface ofthe heat source comprises spraying an atomized liquid spray onto thesurface of the heat source with a pressure atomizer nozzle, whereinpressurized liquid is inputted to the pressure atomizer nozzle.
 8. Themethod according to claim 4, wherein spraying an atomized liquid coolantonto the surface of the heat source comprises spraying an atomizedliquid coolant onto the surface of the heat source with a vapor assistnozzle, wherein pressurized liquid coolant and pressurized vapor coolantis inputted to the vapor assist nozzle.
 9. The method according to claim4, wherein spraying an atomized liquid coolant onto the surface of theheat source comprises spraying an atomized liquid coolant onto thesurface of the heat source with a pressurized vapor nozzle, whereinliquid coolant and vapor coolant is inputted to the pressurized vapornozzle.
 10. The method according to claim 4, wherein spraying anatomized liquid coolant onto the surface of the heat source comprisesspraying an atomized liquid coolant onto the surface of the heat sourcewith a vapor atomizing nozzle, wherein flow of vapor through the vaporatomizing nozzle creates a venturi draft on a liquid coolant sourceinputted to the vapor atomizing nozzle.
 11. The method according toclaim 4, wherein spraying an atomized liquid coolant onto the surface ofthe heat source forms a thin film of coolant on the surface of the heatsource.
 12. The method according to claim 4, wherein the coolant issprayed such that when the atomized liquid coolant is sprayed onto thesurface of the heat source the coolant can begin to boil.
 13. The methodaccording to claim 12, wherein a portion of the coolant which is sprayedonto the surface of the heat source evaporates and a remaining portionof the coolant which is sprayed onto the surface of the heat sourceexits the surface of the heat source out of the subsection due to themomentum of the coolant.
 14. The method according to claim 4, whereinupon spraying an atomized liquid coolant onto the surface of the heatsource, single phase convection, boiling, and/or free surfaceevaporation of the coolant occur.
 15. The method according to claim 14,wherein coolant sprayed onto the surface of the heat source which boilsand/or evaporates is released into the environment.
 16. The methodaccording to claim 4, wherein the surface of the heat source is locatedwithin a sealed housing and wherein spraying an atomized liquid coolantonto the surface of the heat source is within the sealed housing,wherein the method further comprises: releasing the heat absorbed by thecoolant from the surface of the heat source via a condenser.
 17. Themethod according to claim 16, wherein the condenser comprises a heatexchanger.
 18. The method according to claim 16, wherein the condenseroperates via a subcooled mist of the coolant, wherein the sub-cooledmist of the coolant is sub-cooled below the saturation temperature ofthe coolant within the sealed housing via a heat exchanger, wherein theheat exchanger is outside the sealed housing, wherein the subcooled mistis sprayed within the sealed housing so as to contact saturated vapor ofthe coolant evaporating from the surface of the heat source, whereinheat is transferred from the saturated vapor to the sub-cooled mist suchthat the saturated vapor condenses on the sub-cooled mist and flows to areservoir of the coolant.
 19. The method according to claim 1, whereinthe partition wall shared by a subsection with an adjacent subsectionsubstantially eliminates the flow of coolant from the subsection to theadjacent subsection and the flow of coolant from the adjacent subsectionto the subsection.
 20. The method according to claim 1, wherein theplurality of subsections each share a partition wall with each adjacentsubsection.
 21. The method according to claim 20, wherein the partitionwalls are interconnected so as to enclose a portion of the plurality ofsubsections with the interconnected partition walls.
 22. The methodaccording to claim 21, wherein the interconnected partition walls form apattern such that the portion of the plurality of subsections areenclosed by polygonal shaped sections of the interconnected partitionwalls.
 23. The method according to claim 22, wherein the portion of theplurality of subsections are enclosed by rectangular shaped sections ofthe interconnected partition walls.
 24. The method according to claim23, wherein the portion of the plurality of subsections are enclosed bysquare shaped sections of the interconnected partition walls.
 25. Themethod according to claim 22, wherein the portion of the plurality ofsubsections are enclosed by hexagonal shaped sections of theinterconnected partition walls.
 26. The method according to claim 1,wherein spraying an atomized liquid coolant onto the surface of the heatsource comprises spraying an atomized liquid coolant onto the surface ofthe heat source via a single spray nozzle such that the single spraynozzle sprays the atomized liquid coolant through each subsection ontothe surface of the heat source.
 27. The method according to claim 1wherein spraying an atomized liquid coolant onto the surface of the heatsource comprises spraying an atomized liquid coolant onto the surface ofthe heat source via a plurality of spray nozzles such that the pluralityof spray nozzles sprays the atomized liquid coolant through eachsubsection onto the surface of the heat source.
 28. The method accordingto claim 27, wherein each of the plurality of spray nozzles sprays theatomized liquid coolant through a corresponding subsection onto thesurface of the heat source.
 29. The method according to claim 1, whereineach subsection has a cross-sectional area of about 2 cm² or less. 30.The method according to claim 29, wherein each subsection has across-sectional area between about 0.5 cm² and about 2 cm².
 31. Themethod according to claim 1, wherein the partition walls protrude atleast about 0.2 cm from the surface of the heat source.
 32. The methodaccording to claim 31, wherein the partition walls protrude betweenabout 0.2 cm and about 2 cm from the surface of the heat source.
 33. Anapparatus for removing heat from a heat source, comprising: an interfaceplate, the interface plate comprising a plurality of subsections whereineach subsection shares a partition wall with at least one adjacentsubsection, wherein the interface plate is in contact with a surface ofthe heat source, a spray nozzle which directs a spray pattern of theliquid coolant through each subsection onto the surface of the heatsource, wherein the liquid coolant sprayed onto the surface of the heatsource absorbs heat from the surface of the heat source and carries theabsorbed heat away as the coolant leaves the surface of the heat source,wherein the partition wall shared by a subsection with an adjacentsubsection reduces the flow of coolant from the subsection to theadjacent subsection and the flow of coolant from the adjacent subsectionto the subsection.
 34. The apparatus according to claim 33, wherein thespray nozzle atomizes the liquid coolant which is sprayed onto thesurface of the heat source.
 35. The apparatus according to claim 34,wherein the atomized liquid coolant sprayed onto the surface of the heatsource comprises droplets having mean diameters in a range from about 10microns to about 200 microns and velocities in a range from about 5meters per second to about 50 meters per second.
 36. The apparatusaccording to claim 34, wherein the atomized liquid coolant sprayed ontothe surface of the heat source comprises spraying droplets having a sizeand velocity such that the effects of gravity are negligible.
 37. Theapparatus according to claim 34, wherein the spray nozzle comprises apressure atomizer nozzle, wherein pressurized liquid is inputted to thepressure atomizer nozzle.
 38. The apparatus according to claim 34,wherein the spray nozzle comprises a vapor assist nozzle, whereinpressurized liquid coolant and pressurized vapor coolant is inputted tothe vapor assist nozzle.
 39. The apparatus according to claim 34,wherein the spray nozzle comprises a pressurized vapor nozzle, whereinliquid coolant and vapor coolant is inputted to the pressurized vapornozzle.
 40. The apparatus according to claim 34, wherein the spraynozzle comprises a vapor atomizing nozzle, wherein flow of vapor throughthe vapor atomizing nozzle creates a venturi draft on a liquid coolantsource inputted to the vapor atomizing nozzle.
 41. The apparatusaccording to claim 34, wherein the atomized liquid coolant sprayed ontothe surface of the heat source forms a thin film of coolant on thesurface of the heat source.
 42. The apparatus according to claim 34,wherein the coolant is sprayed such that when the atomized liquidcoolant is sprayed onto the surface of the heat source the coolant canbegin to boil.
 43. The apparatus according to claim 42, wherein aportion of the coolant which is sprayed onto the surface of the heatsource evaporates and a remaining portion of the coolant which issprayed onto the surface of the heat source exits the surface of theheat source out of the subsection due to the momentum of the coolant.44. The apparatus according to claim 34, wherein the atomized liquidcoolant sprayed onto the surface of the heat source experiences singlephase convection, boiling, and/or free surface evaporation of thecoolant.
 45. The apparatus according to claim 44, wherein coolantsprayed onto the surface of the heat source which boils and/orevaporates is released into the environment.
 46. The apparatus accordingto claim 34, further comprising a sealed housing and a condenser,wherein the surface of the heat source is located within the sealedhousing and wherein the atomized liquid coolant is sprayed onto thesurface of the heat source within the sealed housing, wherein: the heatabsorbed by the coolant from the surface of the heat source is releasedvia the condenser.
 47. The apparatus according to claim 46, wherein thecondenser comprises a heat exchanger.
 48. The apparatus according toclaim 46, further comprising a heat exchanger, and a reservoir ofcoolant wherein the condenser operates via a sub-cooled mist of thecoolant, wherein the sub-cooled mist of the coolant is sub-cooled belowthe saturation temperature of the coolant within the sealed housing viathe heat exchanger, wherein the heat exchanger is outside the sealedhousing, wherein the sub-cooled mist is sprayed within the sealedhousing so as to contact saturated vapor of the coolant evaporating fromthe first surface, wherein heat is transferred from the saturated vaporto the sub-cooled mist such that the saturated vapor condenses on thesub-cooled mist and flows to the reservoir of the coolant.
 49. Theapparatus according to claim 33, wherein the partition wall shared by asubsection with an adjacent subsection substantially eliminates the flowof coolant from the subsection to the adjacent subsection and the flowof coolant from the adjacent subsection to the subsection.
 50. Theapparatus according to claim 33, further comprising a seal between thepartition wall and the surface of the heat source.
 51. The apparatusaccording to claim 33, wherein the heat source is a power electronicsdevice.
 52. The apparatus according to claim 33, wherein the pluralityof subsections each share a partition wall with each adjacentsubsection.
 53. The apparatus according to claim 52, wherein thepartition walls are interconnected so as to enclose a portion of theplurality of subsections with the interconnected partition walls. 54.The apparatus according to claim 53, wherein the interconnectedpartition walls form a pattern such that the portion of the plurality ofsubsections are enclosed by polygonal shaped sections of theinterconnected partition walls.
 55. The apparatus according to claim 54,wherein the portion of the plurality of subsections are enclosed byrectangular shaped sections of the interconnected partition walls. 56.The apparatus according to claim 55, wherein the portion of theplurality of subsections are enclosed by square shaped sections of theinterconnected partition walls.
 57. The apparatus according to claim 54,wherein the portion of the plurality of subsections are enclosed byhexagonal shaped sections of the interconnected partition walls.
 58. Theapparatus according to claim 33, wherein the spray nozzle comprises asingle spray nozzle such that the single spray nozzle sprays theatomized liquid coolant through each subsection onto the surface of theheat source.
 59. The apparatus according to claim 33, wherein the spraynozzle comprises a plurality of spray nozzles such that the plurality ofspray nozzles sprays the atomized liquid coolant through each subsectiononto the surface of the heat source.
 60. The apparatus according toclaim 59, wherein each of the plurality of spray nozzles sprays theatomized liquid coolant through a corresponding subsection onto thesurface of the heat source.
 61. The apparatus according to claim 33,wherein each subsection has a cross-sectional area of about 2 cm² orless.
 62. The apparatus according to claim 61, wherein each subsectionhas a cross-sectional area between about 0.5 cm² and about 2 cm². 63.The apparatus according to claim 33, wherein the partition wallsprotrude at least about 0.2 cm from the surface of the heat source. 64.The apparatus according to claim 63, wherein the partition wallsprotrude between about 0.2 cm and about 2 cm from the surface of theheat source.